D. Little Pony and Elements of Harmonysolutionei[u]=∑vei−1[v]∗b[f(u,v)].e_i[u]=\sum_{v}e_{i-1}[v]*b[f(u,v)].ei​[u]=v∑​ei−1​[v]∗b[f(u,v)].设 cnt[u⊕v]=b[f(u⊕v)]cnt[u⊕v]=b[f(u⊕v)]cnt[u⊕v]=b[f(u⊕v)]，有：ei[u